Exam 2: Lecture 12

Question 1

what occurs to blood glucose remove during exercise?

Answer 1

it is accelerated

Question 2

how does glucose enter the cell?

Answer 2

GLUT-4 transporter

Question 3

where does most of the carbohydrate used as a substrate during short term exercise (<2 hr) come from?

Answer 3

glycogen stores in the muscle

the remainder comes from blood glucose

Question 4

what determines the rate of glycogen use?

Answer 4

intensity and duration of the exercise

glycogen is broken down faster with heavier exercise

Question 5

what enhances glycogen breakdown?

Answer 5

increases in glucagon, epinephrine, and norepinephrine and decreases in insulin during exercise

Question 6

Short term minute to minute regulation of blood glucose concentration is dependent on what?

Answer 6

Hormones:

• epinephrine
• norepinephrine
• insulin
• glucagon

Question 7

with exercise, activation of sympathetic nerves plus the adrenal medulla release of epinephrine result in:

Answer 7

1. inhibition of insulin release
2. increased secretion of glucagon
3. these hormonal changes favor the breakdown of glycogen, inhibition of glucose storage, and inhibition of lipid storage

Question 8

Glucagon secretion increases during prolonged exercise –> the stimuli include:

Answer 8

1. decreased levels of blood glucose (potentially present during prolonged exercise)
2. increased plasma amino acids (potentially present during prolonged exercise)

Question 9

normal stimuli for insulin release include:

Answer 9

1. high level of blood glucose
2. high level of plasma amino acids
3. high level of free fatty acids
4. high level of parasympathetic nerve activity

Question 10

what predominates during exercise?

Answer 10

the inhibitory effects of high sympathetic activity

insulin levels decrease

Question 11

normal effects of insulin

dont forget it decreases during exercise

Answer 11

1. enhances tissue uptake of glucose via GLUT 4 transporters
2. enhances storage of blood glucose, inhibits breakdown of glycogen, inhibits liver gluconeogenesis
3. stores fat in adipose tissue, inhibits breakdown of triglycerides into FFA

Question 12

normal effects of glucagon

Answer 12

1. increase blood glucose via liver and muscle glycogenolysis and liver gluconeogenesis
2. stimulates lipolysis in fat cells-provide FFA to muscle cells

Question 13

catecholamine effects during exercise (especially epinephrine)

Answer 13

1. stimulate glycogenolysis, gluconeogenesis, lipolysis (same as glucagon)
2. inhibit uptake of glucose by other tissues; forces use of FFA (spares blood glucose)

Question 14

what type of adrenergic receptor is primarily involved in modulating glucose release from the liver?

Question 15

significance of increases in plasma FFA and the glucose-sparing effect

Answer 15

• increased availability of muscle and blood FFA will “spare” muscle glycogen
• active muscle will take up and utilize the FFA preferentially (during light to moderate exercise) and this decrease utilization of glucose/glycogen
• lipolysis is stimulated by low insulin, high glucagon, and high epinephrine

Question 16

Summary of the 4 processes that maintain blood glucose concentration

Answer 16

1. mobilization of glucose from liver glycogen stores (glucagon, epinephrine, low insulin)
2. mobilization of FFA from adipose tissue to spare plasma glucose (glucagon, epinephrine, low insulin)
3. synthesis of new glucose (gluconeogenesis) from amino acids, lactate and glycerol (more important during long duration exercise, stimulated by epinephrine and glucagon)
4. inhibition of glucose entry into cells to force the use of FFA as fuel (catecholamine effect)

Question 17

Muscle glucose uptake during exercise is maintained by:

Answer 17

1. increased glucose delivery (blood flow x plasma concentration)
2. increased gradient for diffusion from plasma to cells (increased rate of use)
3. insulin-independent glucose uptake by active muscle cells (translocation of GLUT-4 to surface of cell)

Question 18

Acute effect of exercise on muscle glucose uptake

Answer 18

normal effect of insulin to stimulate muscle glucose uptake: insulin –> binds to its receptor on cell membrane –> translocation of GLUT 4 transporter to cell membrane –> glucose enters cell

Question 19

3 major effects that muscular contraction has on muscle glucose uptake in active skeletal muscle:
#1

Answer 19

• during the exercise and continuing for several hours post exercise: there is an insulin-independent, contraction-initiated increase in glucose uptake
• this occurs via translocation of pre-formed GLUT 4 transporters to the cell surface

Question 20

3 major effects that muscular contraction has on muscle glucose uptake in active skeletal muscle:
#2

Answer 20

• During 18 hrs post exercise, there is an increase in the insulin sensitivity of the skeletal muscle
• glucose uptake in response to a submax insulin stimulus is enhanced
• due to an increased movement of previously recruited GLUT4 transporters BACK to the membrane

Question 21

3 major effects that muscular contraction has on muscle glucose uptake in active skeletal muscle:
#3

Answer 21

single bout of exercise initiates protein synthesis and results in:

• increased number of GLUT4 transporters in the muscle cell
• takes about 16 hours

Question 22

who is exercise and post exercise enhancement of glucose uptake beneficial for?

Answer 22

• people with type 1 or type 2 diabetes

- regular exercise is widely recommended for control of type 2 diabetes

Question 23

Glucose secretion during exercise helps to maintain glucose availability for working muscle by

Answer 23

mobilizing free fatty acids from adipose tissue

Question 24

what 2 hormones fine tune the glucose regulation during exercise?

Answer 24

cortisol and GH

Question 25

cortisol- released from adrenal cortex

Answer 25

- effects are primarily permissive during acute exercise - during intense exercise, cortisol plasma concentration increases due to an increase in secretion rate - overall cortisol action is to provide fuel for the body during stress

Question 26

major effects of cortisol during exercise

Answer 26

- stimulation of gluconeogenesis by stimulating hepatic enzymes; enhances protein breakdown - stimulation of glucagon secretion- factors glycogenolysis acutely - permissive for the lipolytic actions of epinephrine and GH - antagonism of insulin-depedent glucose uptake by active and non-active tissues (forces use of FFA) - delayed direct stimulation of glycogen synthesis to re-build glycogen stores - after exercise

Question 27

Growth hormone

Answer 27

- overall GH enhances protein synthesis, elevates plasma glucose and increases the use of fatty acids as a fuel source - during exercise plasma growth hormone concentration increases as a function of exercise intensity and duration